1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device and more particularly, it relates to a manufacturing method of a semiconductor device comprising a semiconductor memory in which data is recorded.
2. Description of the Background Art
In order to add a nonvolatile memory such as an EPROM, a flash memory, an EEPROM to a normal CMOS process, it is necessary to add 5 to 10 masks and add additional processes such as CVD, diffusion, ion implantation and photo lithography in general. In addition, although a channel-cut ROM can be easily made, it cannot be deleted. Japanese Unexamined Patent Publication No. 57-66675 discloses a method of accumulating positive charges in a gate oxide film by electron beam drawing at a low voltage without a mask and accumulating negative charges in a gate electrode by electron beam drawing at low voltage in which enhancement type of NMOS is changed to depression type.
As described above, when the nonvolatile memory is mounted on the IC process, since the number of processes is increased, there is a problem such that a cost is increased and a structure becomes complicated so that a yield is lowered. In addition, according to the channel-cut ROM, since deleting and rewriting cannot be performed and a recording operation is necessary in the middle of the process, it is difficult to expand product variation. Furthermore, it takes time to record one bit because a beam current is not provided in the electron beam drawing at a low acceleration energy (several tens of keV), and a required time is increased by the number of bits every time the number of bits to be recorded is increased. Thus, there is a problem such that since the electron beam cannot be controlled when the drawing is performed at high acceleration energy and high current, the recording cannot be performed by one bit a time.